1. Field of the Invention
The present invention relates to an electromagnetic switch to be mounted on a starter for cranking an internal combustion engine, and more particularly to a structure for leading out a conductor member in the electromagnetic switch.
2. Description of Related Art
An electromagnetic switch to be mounted on a starter for cranking an internal combustion engine usually includes a plunger driven by an excitation coil and a movable contact moving in an axial direction of the plunger according to movement of the plunger. Electric current is supplied to the excitation coil from an on-board battery through a conductor member connected to the excitation coil. The conductor member is led out through a molded contact cover and extends outside to be connected to an outside cable connected to the battery through an ignition switch. It is required to connect the conductor member to the outside cable by a screw-fastening or welding without using solder-connection in order to withstand a high vibration transferred from an automotive vehicle. At the same time, the conductor member has to be easily led out from the contact cover in an automated manufacturing process.
To meet these requirements, an electromagnetic switch is proposed in JP-A-2002-313205. In this electromagnetic switch, a lead terminal having a high mechanical strength is used in place of a fragile conductor member for supplying excitation current. Since the lead terminal is led out straight in the axial direction through the contact cover, the electromagnetic switch can be assembled in an automated manufacturing line. In the proposed electromagnetic switch, however, a large connecting portion for electrically connecting the lead terminal to the outside cable cannot be provided at an end of the lead terminal, because the lead terminal has to be led out through a through-hole formed in the contact cover. It is, of course, possible to connect a large connecting portion having a female screw hole to the end of the lead terminal by welding after the process of assembling the switch is completed. However, this requires an additional step in the manufacturing process.
Further, to give a sufficient mechanical strength to the lead terminal against high vibration, it is necessary to use a bulky lead terminal which requires enlargement of the contact cover in size. A portion of the lead terminal led out from the contact cover vibrates in a manner of a cantilever supported at a point leading out the lead terminal. Therefore, the size of the lead terminal cannot be made unreasonably large. Further, if the lead terminal is vibrated due to vibration of the outside cable, there is a possibility that the lead terminal may be disconnected.
Another conductor member structure of the electromagnetic switch is proposed in JP-A-2004-111231. In this structure, an end of the outside cable is connected to a molded cover via an eyelet terminal. If a large stress is imposed on the eyelet terminal, there is a possibility that connection of the eyelet terminal to the molded cover is loosened and a conductor member connected to the excitation coil may be disconnected due to vibration transferred from an engine.